UK Labour leader Mr Starmer called on Mr Johnson to “have the decency” to withdraw a remark made about him relating to the IRA.
The British prime minister accused Mr Starmer of having “supported an IRA-condoning politician” by serving in former Labour leader Jeremy Corbyn’s frontbench team.
Mr Corbyn, who has supported Irish republicanism, said in a 2017 interview with Sky News: “I condemn all the bombing by both the loyalists and the IRA.”
Mr Johnson told the Commons: “This is a leader of the opposition who supported an IRA-condoning politician who wanted to get out of Nato and now says absolutely nothing.”
Mr Johnson’s comments were cut off by Commons Speaker Lindsay Hoyle, who called for order.
Mr Starmer demanded Mr Johnson withdraw his comments relating to the IRA, adding: “Before I go on, the Prime Minister said something about the IRA and I want him to take it back.
“I worked in Northern Ireland for five years with the Police Service of Northern Ireland bringing peace.
“I prosecuted, as director of public prosecutions, serious terrorists – for five years working with the intelligence and security forces and with the police in Northern Ireland.
“I ask the Prime Minister to have the decency to withdraw that comment.”
The Speaker asked if the prime minister wanted to withdraw his allegation he made about Mr Starmer.
Mr Johnson replied: “I listened to the protestations of the right honourable gentleman and think they would have been more in order throughout the long years in which he supported a leader of the Labour Party [Mr Corbyn]…”
Mr Hoyle then signalled for Mr Johnson to sit down.
In response, Mr Starmer said: “When the Prime Minister has worked with the intelligence and security forces prosecuting criminals and terrorists he can lecture me.
“I asked him to do the decent thing, but doing the decent thing and this Prime Minister don’t go together.”
